Thieves can't imbue, I think the reasoning behind it was they already had so many unique advantages (poisons, barbs, stealing from houses, the black market) that they figured it would be unbalanced or something. I'm pretty sure that's why, don't quote me on it though.

Bolvar Fordring - Elven NecromancerJamendithas D'jmare - Elven Wizard"Ulric the Just! The devil bear has stolen my wife!""This will not stand! I bring you the devil bear's wife.""But.. Ulric.. I kinda wanted my own wife back...""You have no concept of justice, enjoy your new wife."